Protective padding utilizing superelastic three-dimensional spacer fabric comprising shape memory materials (smm)

ABSTRACT

Protective padding comprising:
         a spacer fabric comprising a first fabric layer, a second fabric layer, and a plurality of interconnecting filaments extending between said first fabric layer and said second fabric layer;   wherein at least one of said first fabric layer, said second fabric layer and said plurality of interconnecting filaments comprise a shape memory material.

REFERENCE TO PENDING PRIOR PATENT APPLICATIONS

This patent application:

-   -   (i) is a continuation-in-part of pending prior U.S. patent        application Ser. No. 13/843,656, filed Mar. 15, 2013 by Matthew        Fonte et al. for DYNAMIC POROUS COATING FOR OTHOPEDIC IMPLANT        (Attorney's Docket No. FONTE-15171824), which patent        application (a) is a continuation-in-part of prior U.S. patent        application Ser. No. 13/764,188, filed Feb. 11, 2013 by Matthew        Fonte et al. for POROUS COATING FOR ORTHOPEDIC IMPLANT UTILIZING        POROUS, SHAPE MEMORY MATERIALS (Attorney's Docket No. FONTE-15),        which patent application claims benefit of prior U.S.        Provisional Patent Application Ser. No. 61/596,900, filed Feb.        9, 2012 by Matthew Fonte et al. for POROUS, SHAPE MEMORY        MATERIAL, ORTHOPEDIC IMPLANT COATING (Attorney's Docket No.        FONTE-15 PROV); (b) claims benefit of prior U.S. Provisional        Patent Application Ser. No. 61/612,496, filed Mar. 19, 2012 by        Matthew Fonte et al. for POROUS, SHAPE MEMORY MATERIAL,        ORTHOPEDIC IMPLANT COATING (Attorney's Docket No. FONTE-17        PROV); (c) claims benefit of prior U.S. Provisional Patent        Application Ser. No. 61/661,086, filed Jun. 18, 2012 by Matthew        Fonte et al. for “DYNAMIC” ORTHOPEDIC COATINGS MADE OF SPACER        FABRIC (Attorney's Docket No. FONTE-18 PROV); and (d) claims        benefit of prior U.S. Provisional Patent Application Ser. No.        61/738,574, filed Dec. 18, 2012 by Matthew Fonte et al. for        POROUS, SHAPE MEMORY MATERIAL, ORTHOPEDIC IMPLANT COATING        (Attorney's Docket No. FONTE-24 PROV);    -   (ii) is a continuation-in-part of pending prior U.S. patent        application Ser. No. 13/936,866, filed Jul. 8, 2013 by Matthew        Fonte et al. for INSOLE AND FOOT ORTHOTICS MADE OF SHAPE MEMORY        MATERIAL (SMM) THREE-DIMENSIONAL SPACER FABRICS (Attorney's        Docket No. FONTE-2021), which patent application (a) is a        continuation-in-part of the aforementioned U.S. patent        application Ser. No. 13/843,656 and claims benefit of the        aforementioned prior U.S. patent applications Ser. Nos.        13/764,188, 61/596,900, 61/612,496, 61/661,086, and 61/738,574,        and (b) claims benefit of prior U.S. Provisional Patent        Application Ser. No. 61/668,732, filed Jul. 6, 2012 by Matthew        Fonte et al. for SHOE INSOLE AND FOOT ORTHOTICS MADE OF SHAPE        MEMORY MATERIAL THREE-DIMENSIONAL SPACER FABRICS (Attorney's        Docket No. FONTE-20 PROV), and (c) claims benefit of pending        prior U.S. Provisional Patent Application Ser. No. 61/671,129,        filed Jul. 13, 2012 by Matthew Fonte et al. for SUPERELASTIC        THREE-DIMENSIONAL SPACER FABRIC USING SHAPE MEMORY MATERIALS        (Attorney's Docket No. FONTE-21 PROV); and    -   (iii) claims benefit of pending prior U.S. Provisional Patent        Application Ser. No. 61/671,129, filed Jul. 13, 2012 by Matthew        Fonte et al. for SUPERELASTIC THREE-DIMENSIONAL SPACER FABRIC        USING SHAPE MEMORY MATERIALS (Attorney's Docket No. FONTE-21        PROV).

The nine (9) above-identified patent applications are herebyincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to protective padding in general, and moreparticularly to improved approaches for absorbing shock and distributingforces in protective padding.

BACKGROUND OF THE INVENTION

Protective padding is well known for protecting the body against impact,e.g., during sporting events, hazardous activities, military situations,etc.

Foam materials such as neoprene and polyurethane are often used inprotective padding applications, due to their ability to providecushioning, compression, stability, resilience, elasticity and/orflexibility. Foam may be open-cell or closed-cell in nature. Open-cellfoam has air pockets that are connected to each other. Closed-cell foamhas air pockets that form unconnected discrete voids within the foam.One major drawback of such open-cell and closed-cell foam materials isthat they are largely impermeable to gases and liquids. This can beundesirable where foams are used in applications that come in contactwith the body. For example, Neoprene foams (see FIG. 1) used tostabilize a limb or a joint do not breathe well and can trap moisture,which can lead to infections. In an effort to counter this problem,attempts have been made to perforate foam sheets so as to increase theirbreathability; however, such perforation decreases the mechanicalproperties of the foam, which can undermine the effectiveness of thefoam. Furthermore, the repeated application of a load causes foam to“wear out” over time and loose the resilient properties which made themuseful in the original application.

Spacer fabrics were developed to address the inadequacies of foams.Spacer fabrics are manufactured using knitting or weaving techniques,are elastic in structure, and have been employed in many applicationsincluding clothing, mattresses, seats, and patient-support materials inthe medical industry.

As seen in FIG. 2, a three-dimensional knit spacer fabric 5 includes afirst fabric layer 10, a second fabric layer 15 and yarns 20interconnecting the two layers 10, 15. Some of the yarns 20interconnecting the two layers 10, 15 are substantially perpendicular tothe first and second fabric layers 10, 15, while the remaininginterconnecting yarns 20 are disposed at an acute angle between the twolayers 10, 15.

Knit manufacturing is the most common method for producing spacerfabrics. The double-face spacer fabric 5 is prepared by knitting athree-dimensional knit fabric on a double-needle bar warp knittingmachine commonly used in the manufacture of velvet. A synthetic materialsuch as polyester, acrylic or nylon is used to form the yarn which isknit into the spacer fabric construct. The yarn may be a filament orspun, textured or fully oriented. The yarn 20 interconnecting the twolayers 10, 15 of the spacer fabric 5 has sufficient resilience andstiffness to keep the two fabric layers 10, 15 separated from oneanother when pressure is applied to either (or both) of the construct'sfabric layers 10, 15.

The interconnecting pile yarns 20 can be made of the same or differentmaterials from that of the two surface fabric layers 10, 15. The twosurface fabric layers 10, 15 can be made of the same material or theycan be made of different materials. More particularly, in order torender the interconnecting pile yarns 20 resilient, the yarns 20 may bemade of a resilient material such as a monofilament or multifilamentpolyester or nylon.

By changing one or more of (i) the material(s) used to form the spacerfabric, (ii) the thickness(es) (i.e., diameter(s)) of the filamentsused, and (iii) the space between fabric layers 10, 15, the materialproperties of the spacer fabric 5 can be altered. A thicker spacerfabric manufactured using finer gauge filaments is generally morecompliant than a thinner spacer fabric manufactured from thickerfilaments. Additionally, the pore size of the top and bottom layers 10,15 can be altered by changing the needle spacing and the thickness(es)of the filament(s) used. See FIG. 3.

Thus, spacer fabrics address many of the inadequacies of traditionalfoams. The highly porous nature of spacer fabrics allows them to haveexcellent fluid flow and thermal properties. Spacer fabrics are highlytailorable to specific applications, and are cost-effective since theyuse a low-cost starting plastic material. See FIG. 4

The primary disadvantage of polymeric spacer fabrics is that plasticsare relatively weak, are prone to creep, suffer from fatigue degradationand exhibit permanent compression set. More particularly, and lookingnow at FIG. 5, when a plastic material is subjected to a constant load,it deforms continuously. The initial strain is roughly predicted by itsstress-strain modulus. The plastic material will continue to deformslowly with time, indefinitely, until rupture or yielding causesfailure, e.g., permanent set. As seen in the graph shown in FIG. 5, theinitial region is the early stage of loading when the creep ratedecreases rapidly with time. Then it reaches a steady state, which iscalled the secondary creep stage, followed by a rapid increase (tertiarystage) and fracture. This phenomenon of deformation under load with timeis called creep. Some materials do not have the aforementioned secondarystage, while tertiary creep only occurs at high stresses and for ductilematerials. All plastics creep to a certain extent. The degree of creepdepends on several factors, such as the type of plastic, whether thematerial is wet or dry, the magnitude of the load, the cyclical loadrate, the temperature of the material and the time duration of theapplied load. The standard test method for creep characterization isASTM D2990.

Thus, while protective padding formed out of foam has proven generallybeneficial, it tends to suffer from poor gas and liquid permeability,and loss of resiliency over time. Furthermore, while protective paddingformed out of polymer spacer fabrics have proven generally beneficial,they tend to suffer from overall weakness, creep, fatigue degradationand permanent compression set.

SUMMARY OF THE INVENTION

As noted above, spacer fabrics are a generic term for three dimensionalfabrics that have a first fabric layer, a second fabric layer, and anintervening fabric layer that interconnects the first fabric layer tothe second fabric layer. Spacer fabrics are used commonly in manyindustries, and are often used in applications where fluid flow,cushioning, and vibration absorption are necessary. Spacer fabrics maybe manufactured using knitting or weaving techniques. Currently, spacerfabrics are manufactured using monofilament polymeric yarns, orpolyamide or polyester fibers. These materials are highly flexible, kinkresistant, and common in the textile field. However, polymer spacerfabrics suffer from weakness, creep, fatigue degradation and permanentcompression set.

The present invention relates to the provision and use of spacer fabricswhich utilize a shape memory material (SMM), e.g., Nitinol or a titaniumnear-beta alloy, as a filament for constructing the spacer fabric (e.g.,as a filament for constructing the top fabric layer, the bottom fabriclayer and the intervening fabric layer that interconnects the top fabriclayer to the bottom fabric layer). See FIG. 6. SMMs, unlike othermetallic filaments, are highly flexible and kink resistant, allowingthem to be woven or knit. SMM filaments are substantially stronger thanpolymer monofilaments, and are not susceptible to deleterious creep andfatigue which often shortens the life of polymeric materials. Spacerfabrics created from shape memory materials (SMM) can be designed to bestrong, superelastic, exhibiting a hysteresis for large shape recoverystrains and can be designed to change shape based on temperaturechanges.

More particularly, the present invention relates to the provision anduse of shape memory material (SMM) spacer fabrics for protectivepadding. Since shape memory material (SMM) spacer fabrics are elasticand compressible, and do not suffer from the disadvantages associatedwith plastic deformation discussed above, their resilient structuremakes them ideal for protective padding applications where a force mustbe dampened. The resilient nature of shape memory material (SMM) spacerfabrics permits them to absorb and dampen impact without sufferingpermanent deformation or loss of resiliency. Thus, shape memory material(SMM) spacer fabrics are ideally suited for protective paddingapplications.

In one preferred form of the present invention, there is providedprotective padding comprising:

-   -   a spacer fabric comprising a first fabric layer, a second fabric        layer, and a plurality of interconnecting filaments extending        between said first fabric layer and said second fabric layer;    -   wherein at least one of said first fabric layer, said second        fabric layer and said plurality of interconnecting filaments        comprise a shape memory material.

In another preferred form of the present invention, there is providedprotective padding comprising:

-   -   an outer surface;    -   an inner surface; and    -   a spacer fabric disposed between said outer surface and said        inner surface, said spacer fabric comprising a first layer, a        second layer, and a plurality of interconnecting filaments        extending between said first layer and said second layer;    -   wherein at least one of said first layer, said second layer and        said plurality of interconnecting filaments comprise a shape        memory material.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which is tobe considered together with the accompanying drawings wherein likenumbers refer to like parts, and further wherein:

FIG. 1 is a schematic view showing a neoprene foam sheet;

FIG. 2 is a schematic view showing a conventional polymer spacer fabric,with the spacer fabric being compressed;

FIG. 3 is a schematic view showing various conventional polymer spacerfabrics with different mechanical properties;

FIG. 4 is a schematic view showing how three-dimensional spacer fabricscomprise multiple discrete layers, are lightweight, breathable, willwick away moisture and will cool or insulate;

FIG. 5 is a schematic view showing creep behavior for polymer materials;

FIG. 6 is a schematic view showing a spacer fabric made from shapememory material;

FIG. 7 is a schematic view showing a spacer fabric made from Nitinol;

FIG. 8 is a schematic view showing the stress-strain curves for steeland Nitinol;

FIG. 9 is a schematic view showing the damping capacity of Nitinol,aluminum, stainless steel and brass as a function of temperature;

FIG. 10 is a schematic view showing the storage modulus capacity ofNitinol, aluminum, stainless steel and brass as a function oftemperature;

FIG. 11 is a schematic view showing the stress-strain diagram for bone,Nitinol and stainless steel;

FIG. 12 is a schematic view showing a double needle bar warp knittingmachine for the production of Nitinol spacer fabrics;

FIG. 13 is a schematic view showing how superelastic spacer fabrics canbe layered on top of each other;

FIG. 14 is a schematic view showing the formation of stress-inducedmartensite;

FIG. 15 is a schematic view showing the use of Nitinol spacer fabric toform protective padding for a helmet;

FIG. 16 is a schematic view showing the use of Nitinol spacer fabric toform protective padding for a lacrosse application;

FIG. 17 is a schematic cross-sectional view showing protective paddingformed out of shape memory material (SMM) spacer fabric;

FIG. 18 is a schematic view showing the use of Nitinol spacer fabric toform protective padding for a football application;

FIG. 19 is a schematic view showing the use of Nitinol spacer fabric toform protective padding for a hockey application; and

FIG. 20 is a schematic view showing the use of Nitinol spacer fabric toform protective padding for a mountain biking application.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, there is provided novelprotective padding utilizing superelastic three-dimensional spacerfabric comprising shape memory materials (SMMs) such as Nitinol. Thesuperelastic vertical fibers of the spacer fabric (i.e., theinterconnecting yarns which extend between the top fabric layer and thebottom fabric layer) create the desired elastic response in the spacerfabric when compressed by an outside force and allowed to shape recover,which addresses the deficiencies of the prior art.

See FIG. 7, which shows a three-dimensional knit spacer fabric 105includes a first fabric layer 110, a second fabric layer 115 and yarns120 interconnecting the two layers 110, 115, wherein some of the yarns120 interconnecting the two layers 110, 115 are substantiallyperpendicular to the first and second fabric layers 110, 115, while theremaining interconnecting yarns 120 are disposed at an acute anglebetween the two layers 110, 115, and further wherein at least the yarns120 are formed out of a shape memory material (SMM) such as Nitinol.

In one preferred form of the invention, first fabric layer 110, secondfabric layer 115 and interconnecting filaments 120 are all formed out offilaments made from a shape memory material (SMM) such as Nitinol.

In another preferred form of the invention, interconnecting yarns 120are formed out of shape-memory material such as Nitinol, and firstfabric layer 110 and second fabric layer 115 are formed out filamentsmade from a non-shape memory material (SMM).

With shape-memory metals such as Nitinol, pseudoelasticity, sometimescalled superelasticity, is an elastic (reversible) response to anapplied stress, caused by a phase transformation between the austeniticand martensitic phases of a crystal. Pseudoelasticity is from thereversible motion of domain boundaries during the phase transformation,rather than just bond stretching or the introduction of defects in thecrystal lattice (thus it is not true superelasticity but ratherpseudoelasticity). Even if the domain boundaries do become pinned, theymay be reversed through heating. Thus, a pseudoelastic material mayreturn to its previous shape (hence, shape memory) after the removal ofrelatively high applied strains. One special case of pseudoelasticity iscalled the Bain Correspondence which involves theaustenite-to-martensite phase transformation between a face-centeredcrystal lattice and a body-centered tetragonal crystal structure.

Superelastic alloys belong to the larger family of shape-memory alloys.When mechanically loaded, a superelastic alloy deforms reversibly tovery high strains—up to 10%—by the creation of a stress-induced phase(i.e., stress-induced martensite). When the load is removed, the new(i.e., stress-induced) phase becomes unstable and the material regainsits original shape. Unlike shape-memory alloys that utilize shape memoryeffect, in superelasticity no change in temperature is needed for thealloy to recover its initial shape. Superelastic devices take advantageof their large, reversible deformation. Superelastic products includeantennas, eyeglass frames and biomedical stents.

Among other things, the present invention provides a dynamic spacerfabric made of metallic shape memory material (SMM) that has vastlyimproved fatigue life compared to polymeric alternatives. Metal andpolymeric fatigue is the progressive and localized structural damagethat occurs when a material is subjected to cyclic loadings. Among otherthings, metals and polymers are different in the fact that polymers areviscoelastic and commonly show hysteretic elastic effects. Most metals,however, tend to only have linear elastic behavior. Yet the relationshipbetween stress or strain amplitude and fatigue life are asserted forpolymers in the same way as for metals. Most polymeric materials exhibitvastly less endurance fatigue levels compared to structural metals,i.e., steel, stainless steel, titanium and Nitinol (nickel-titaniumalloy).

It is the polymer's hysteretic elastic effects that make the spacerfabric structure so resilient to compressive set.

While in most engineering materials load increases with deflection uponloading in a linear way, and decreases along the same path uponunloading, shape memory metals (e.g., Nitinol) exhibit a distinctlydifferent behavior, i.e., they have a hysteretic elastic behavior likeweak polymers but large strength like metals.

Looking now at FIG. 8, with Nitinol, upon loading, stress firstincreases linearly with strain up to approximately 1% strain. After afirst “yield point”, several percent strain can be accumulated with onlya small stress increase. The end of this plateau (“loading plateau”) isreached at about 8% strain. After that, there is another linear increaseof stress with strain. Unloading from the end of the plateau regioncauses the stress to decrease rapidly until a lower plateau (“unloadingplateau”) is reached. Strain is recovered in this region with only asmall decrease of stress. See FIG. 8.

Nitinol exhibits a hysteresis stress-stain curve allowing for 8% shaperecovery before permanent set, a degree of shape recovery which isunique for metals. The last portion of the deforming strain is finallyrecovered in a linear fashion again. The unloading stress can be as lowas 25% of the loading stress. For comparison, the straight linerepresenting the linear elastic behavior according to Hook's law forsteel is also shown in FIG. 8.

Nitinol has a hysteresis stress-strain curve similar to polymers butunique to metals. When the spacer fabric is made of strong Nitinol, itcan support heavy loads, eventually deflect under these weight-bearingloads and cushion the loads, and then recover its shape when the loadsare removed.

In one preferred form of the invention, the Nitinol spacer fabric 105has enhanced cushion energy (CE), enhanced cushion factor (CF) andenhanced resistance to dynamic compression as compared to polymer spacerfabrics. Cushion energy (CE) is the energy required to graduallycompress a specimen of the material up to a standard pressure with atensile-compression testing machine. Cushion factor (CF) is a bulkmaterial property and is assessed using a test specimen greater thansixteen millimeters thick. The pressure on the surface of the testspecimen at a pre-defined loading is multiplied by the volume of thetest specimen under no load. This pressure is then divided by thecushion energy (CE) of the specimen at the pre-defined load. Lastly, theresistance to dynamic compression measures changes in dimensions and incushion energy (CE) after a prolonged period of dynamic compression.

And in one particularly preferred form of the present invention, thespacer fabric comprises a shape memory material (e.g., Nitinol) that iskink resistant. Unlike most metals, Nitinol wires have a unique qualityof being kink resistant. These wires can be bent 10 times more thanstainless steel wires can be bent without experiencing permanentdeformation. For example, a 0.035 inch Nitinol wire can be wrappedaround a 0.50 inch diameter mandrel without taking a set, while astainless steel wire of the same diameter can only be bent around a 5inch diameter mandrel without taking a set or being plasticallydeformed.

Kink resistance is an important feature of Nitinol spacer fabrics whenbeing produced on the double bar knitting machines. Other metals willnot allow for tight radii bending during knitting without kinking,however, Nitinol does allow for tight radii bending during knittingwithout kinking. In application, Nitinol spacer fabric can be completelycompressed (crushed) flat and will return to its original height whenthe deforming force is removed without kinking. Other structural metalssuch as steel, stainless steel and titanium will kink after beingcrushed.

In another preferred form of the present invention, the Nitinol spacerfabric has enhanced dampening and cushioning characteristics compared toother metals, and even polymers, by exploiting the shape memorymaterial's unique ability to recover large strains due to a solid-solidphase transformation and to dissipate energy because of the resultinginternal friction.

It is known that the high damping capacity of the thermoelasticmartensitic phase of Nitinol is related to the hysteretic movement ofcrystallographic interfaces in the alloy (martensite variant interfacesand twin boundaries). Also, the damping capacity of a shape memorymaterial (SMM) depends directly on external variables such as heatingrate, frequency and oscillation amplitude; and internal variables suchas the type of material, grain size, martensite interface density andstructural defects. In Nitinol, a high damping capacity and a lowstorage modulus in the martensitic state is observed. It has beenverified that during phase transformation, there is the presence of apeak in damping capacity and an equivalent increase of storage modulus.The storage modulus, represented by the elastic component and related toa material's stiffness.

A comparative study on the dynamic properties of structural materialswas carried out and clearly demonstrates the superior damping behaviorof shape memory alloy (SMA) Nitinol over classical structural materialsunder the same external conditions. Among other things, Nitinol (NiTi)shape memory alloy (SMA) specimens were compared to commercial aluminum,stainless steel and brass as samples of classical materials. All beamspecimens were submitted to Dynamic Mechanical Analysis (DMA) testsusing a commercial apparatus in a single cantilever mode undertemperature variation. Damping capacity and storage-modulus variationwere analyzed.

Dynamic modulus is the ratio of stress-to-strain under vibratoryconditions calculated from data obtained from either free or forcedvibration tests, in shear, compression or elongation. It is a propertyof viscoelastic materials. The storage modulus and loss modulus inviscoelastic solids measure the stored energy, representing the elasticportion, and the energy dissipated as heat, representing the viscousportion, respectively. Damping behavior of all specimens were observed,with the NiTi SMA, aluminum, stainless steel and brass specimens beingsubmitted to a temperature ramp of 5° C./min with a frequency of 1 Hzand 5 μm of oscillation amplitude. See FIG. 9.

The NiTi SMA showed, in the martensitic state (between room temperatureand about 70° C.), a higher damping capacity in comparison with theother studied materials. This difference in damping capacity increaseseven more in the phase transformation temperature range (between 70° C.and 90° C.), when the NiTi specimen presents a significant peak in itsdamping capacity; while aluminum, stainless steel and brass samplespresent relatively modest, incremental increases. For temperatureshigher than 90° C., the NiTi SMA is fully in the austenitic state, whichintrinsically presents smaller energy absorption than the martensiticstate. The fact that the NiTi SMA alloy is in its fully austenitic stateexplains the decrease in its damping capacity in this temperature range,as compared to the NiTi SMA alloy when it is in its martensitic state.Better damping capacity values can also be obtained from the NiTi SMA asthe oscillation amplitude and/or frequency decreases and as the heatingrate increases.

The storage modulus variation is better visualized in relation to roomtemperature. While a reduction of 5% is perceived in classicalmaterials, a clearly superior increase of about 17% occurs in NiTi SMA.See FIG. 10.

The nickel-titanium ratio of Nitinol can be modified to lower the phasetransformation temperature to keep the material martensitic betweenfreezing and 90° C.

This comparative study has shown the high damping capacity of NiTi SMAin the martensitic state and during phase transformation. Even betterdamping values can be obtained from NiTi SMA as the oscillationamplitude, frequency and heating rate varies. The study also showed asignificant increase in storage modulus during phase transformation.

Nitinol can be very useful when designing a spacer fabric that requiresstiffness control, since the phase transformation is reversible. Bycontrast, classic structural materials (e.g., stainless steel, aluminum,brass, etc.) present an almost-linear increase in damping capacity andsimilar decrease in storage modulus. Other metals and polymers do nothave this unique phase transformation and therefore will not provide aspacer fabric construct with an improved storage modulus due to ashock-absorbing attenuation from hysteresis.

Nitinol is characterized by a specific stress-strain diagram that isdifferent from the deformation behavior of conventional materials.Typical stress-strain diagrams for stainless steel, NiTi alloy, andliving tissues are illustrated. See FIG. 11. In the case of stainlesssteel, the elastically recovered strain (linear portion) is lower than0.5%. Once the elastic limit is exceeded, stainless steel yields(dislocation slip) and considerable increase in strain is achieved. Thisincrease in strain, where the metal appears to flow like a viscousliquid, is called plastic deformation and allows the materials toacquire a permanent set that cannot be recovered after the stress isreleased.

In one preferred form of the invention, the protective padding isconstructed out of a shape memory material which is engineered tooscillate between phase transformations so as to maximize its peakdampening characteristics and storage modulus.

In shape memory materials (SMMs) like Nitinol, early deformation is alsolinearly proportional to the applied stress. Thereafter, deformationcontinues without a significant increase in the force (upper loadingplateau). During unloading, the constraining force is again constantover a wide range of shapes (unloading plateau). Up to 8% of deformationis recoverable in Nitinol. When NiTi is used as a spacer fabric, thefibers are superelastic and the three dimensional structure can recoverup to 100% of its shape after being compressed.

Further details of the present invention are described below.

Shape Memory Material (SMM) Spacer Fabric

As noted above, spacer fabrics are two separate fabrics faces, usuallyknitted independently and then connected by a separate filler spacerfiber. See, for example, FIG. 7, which shows a three-dimensional knitspacer fabric 105 which includes a first fabric layer 110, a secondfabric layer 115 and yarns 120 interconnecting the two layers 110, 115,wherein some of the yarns 120 interconnecting the two layers 110, 115are substantially perpendicular to the first and second fabric layers110, 115, while the remaining interconnecting yarns 120 are disposed atan acute angle between the two layers 110, 115, and further wherein atleast the yarns 120 are formed out of a shape memory material (SMM) suchas Nitinol. In one preferred form of the invention, first fabric layer110, second fabric layer 115 and interconnecting filaments 120 are allformed out of a shape memory material (SMM) such as Nitinol.

The SMM spacer fabric 105 can be produced on both circular and flatknitting machines, using either warp or weft techniques. They may beproduced as a flat sheet, or as a cylindrical tube.

As seen in FIG. 12, a double needle bar warp knitting machine can beused to produce Nitinol spacer fabrics.

SMM spacer fabrics have three distinct layers. The three-ply SMMstructures have good breathability, wettability, crush resistance, and a3D porous appearance. Each layer of the SMM spacer fabric can be made ofdifferent materials and have different porosity levels and geometry.These SMM spacer fabrics can be stacked on one another to form amulti-level spacer fabric construct. See FIG. 13, which shows amulti-level spacer fabric construct 125 comprising a first layer 130, asecond layer 135, a plurality of interconnecting filaments 140 extendingbetween the first and second layers 130, 135, a third layer 145, afourth layer 150, and a plurality of interconnecting filaments 155extending between the third and fourth layers 145, 150, etc.

Additionally, it is possible to knit a multi-level spacer fabric usingspecialized equipment.

The SMM spacer fabric can be designed to have an overall porosityranging from 10% to 98%, with pore sizes ranging from 100-5000 micronsdepending on the application. The modulus of elasticity of thisstand-alone SMM spacer fabric material can be engineered to have amodulus between 25 and 100 kN/m. The SMM spacer fabric material can bedesigned to deform almost 100% under an applied load.

The diameter of the starting fiber greatly determines the mechanicalproperties of the final SMM spacer fabric structure. Thicker fibersresult in a stiffer final construct. The upper limit for the fiberdiameter is determined by the knitting machine being used. Preferably,the diameter of the fiber is between 0.05 inch and 0.0002 inch. Mostpreferably, the fiber is between 0.01 inch and 0.003 inch.

A SMM spacer fabric is superelastic (SE), meaning that if it isdeformed, it is capable of returning to its original shape once thedeforming force is removed. Additionally, a SMM spacer fabric canexhibit a shape memory effect (SME), meaning that it can be dynamicunder the influence of temperature change, i.e., body temperature. As anexample of an SME application, the dynamic spacer fabric can be in acompressed state at a temperature below body temperature (37° C.), andafter being heated above body temperature, return to its original shape.

Polyester, a typical polymeric material used in spacer fabrics, has astiffness of 2 GPa, and a tensile strength of 80 MPa. Nitinol hassuperior mechanical properties to polyester. Nitinol has an austeniticmodulus of 83 GPa, and an austenitic tensile strength of 690 MPa.Nitinol can form a weaker stress-induced martensite phase atapproximately 400 MPa (58,000 PSI). It is possible to engineer the shapememory material spacer fabric construct so that its superelastic regimetoggles between martensite and austenite phases for enhanced dampeningcharacteristics. See FIG. 14.

SMM spacer fabric is also advantageous when used for custom protectivepadding. Instead of having to scan a patient's anatomy and custommachine the custom protective padding, custom SMM spacer fabric can bemade by shape setting the SMM spacer fabric. In one example of this,where the custom protective padding is to be used in a helmet, thepatient presses their head against a “bed” of stainless steel pins,deforming the stainless steel pins to the geometry of their head. Thefar side of the stainless steel pins presses against the SMM spacerfabric, deforming the SMM spacer fabric to the shape of the head. Thestainless steel pins can then be locked into place against the SMMspacer fabric, and the patient's head removed from the “bed” ofstainless steel pins. The deformed SMM spacer fabric can then be heatedto 450° C. for 2 minutes and quenched so that, when the stainless steelpins are removed, the spacer fabric will permanently hold this shape.The heating to shape-set the SMM spacer fabric can also be accomplishedby applying a current to the SMM spacer fabric and heating it throughresistive heating effects. This represents a much more rapid and costeffective method for producing custom protective padding.

The SMM spacer fabric can also be impregnated with a gel, such as asilicone gel, and/or other various polymeric materials. The metallicspacer fabric acts as a spring, absorbing the energy imparted throughthe SMM spacer fabric during impact (e.g., when hit by a ball, a stick,etc.). The SMM spacer fabric also provides cushioning, by supporting thesurface area of the adjacent anatomy. The gel material (or otherimpregnating material) acts as a damper, dissipating this energyefficiently. The SMM spacer fabric can give support to the gel (or otherimpregnating material) so as to increase its stiffness and fatigueendurance limit and can be viewed as somewhat analogous to the use ofrebar and mesh in concrete. The gel (or other impregnating material) canbe made with Shore 00 hardness of 30 (Extra Soft) to a Shore D hardnessof 30 (Hard). Additionally, impregnating the SMM spacer fabric with thegel or other material keeps the individual wires of the SMM spacerfabric in place. Thus, if SMM spacer fabric should be cut during use,fraying of the Nitinol spacer fabric can be mitigated.

Alternatively, a polymeric material that exhibits a solid-to-viscousfluid transition under applied load can be used to impregnate the spacerfabric. One example of such a polymer is Ultra High Molecular WeightPolyethelyne (UHMPE). Energy from the impact of an object is absorbed bythe solid UHMPE. The peak force of impact causes the solid UHMPE toundergo a phase change and become liquid. The energy from the loading ofthe protective padding is absorbed by the UHMPE, and the wearerexperiences increased cushioning from this effect. As the protectivepadding is unloaded, the liquid UHMPE reverts back to the solid state,and is ready for the next impact.

The SMM spacer fabric can be coated with a thin layer of silver toimpart antifungal and antibacterial properties. In one preferredembodiment of the invention, the silver is electrochemically coated ontothe SMM spacer fabric. Alternatively, the layer of silver can bedeposited using a chemical or physical vapor deposition method.

The silver coating can also be applied to the Nitinol wire beforeNitinol wire is knit into the spacer fabric construct. The Nitinol wirecan be plated with silver using one of the aforementioned techniques.Alternatively, the silver-coated Nitinol wire can be created by drawinga metal on metal composite (e.g., a Nitinol core and a silver outertube) so as to create the final silver-coated Nitinol wire.

If desired, the SMM spacer fabric can be coated with a polymer coatingsuch as Teflon (PTFE) so as to change the texture of the spacer fabric(i.e., to make it smooth and give it a plastic feel instead of ametallic feel). In this form of the invention, the polymer coating canbe applied to the entire spacer fabric, or the polymer coating can beapplied to only selected portions of the spacer fabric (e.g., to theouter fabric layer, the inner fabric layer, and/or to theinterconnecting filaments which extend between the outer fabric layerand the inner fabric layer). Alternatively, the polymer coating can beapplied to the Nitinol wire before the Nitinol wire is knit into thespacer fabric construct.

Use Of SMM Spacer Fabric For Protective Padding

A SMM spacer fabric can be used for protective padding in variousapplications.

By way of example but not limitation, SMM spacer fabric can be used toform a helmet lining. More particularly, FIG. 15 illustrates a helmet200 comprising a hard outer shell 205 (which may be made out of metal, ahard plastic, etc.), a fabric harness 210 for seating helmet 200 on thehead of a wearer, and a gap 215 located between fabric harness 210 andthe inside surface of hard outer shell 205. SMM spacer fabric 105 isdisposed within gap 215, interposed between the inside surface of hardouter shell 205 and fabric harness 210, e.g., with first fabric layer110 being disposed adjacent to (or attached to) the inside surface ofhard outer shell 205 and second fabric layer 115 being disposed adjacentto (or attached to) fabric harness 210, and with yarns 120 spanning thedistance between first fabric layer 110 and second fabric layer 115. Byinterposing SMM spacer fabric 105 between fabric harness 210 and hardouter shell 205, a protective padding layer is provided, whereby toprotect the head of a wearer from impact. Thus, when hard outer shell205 of helmet 200 is impacted by a force, the resilient SMM spacerfabric compresses, whereby to absorb the force and protect the head ofthe wearer from injury.

If desired, helmet 200 can be in the form of a military helmet, wherebyto protect a soldier from blast injury, etc., or helmet 200 can be inthe form of a sports helmet (e.g., a football helmet, a hockey helmet, abicycle helmet, etc.), whereby to protect an athlete from impact injury.

In this example, the stiffness of the SMM spacer fabric can be modifiedso as to provide sufficient protection to a wearer's head, with theforce of impact being attenuated by the SMM spacer fabric's dampeningconstruct. Additionally, the SMM spacer fabric can be heat set, i.e., byresistive heating, so as to contour to the wearer's head for a betterfit. By increasing the surface area of the skull that is in contact withthe SMM spacer fabric, the impact forces can be dissipated and desirablylessened over a larger area.

Superelastic spacer fabrics can also be incorporated into variousprotective padding for other sporting applications. See, for example,FIGS. 16 and 17, which illustrate body padding 220 (e.g., for lacrosse).Such body padding 220 may comprise a protective torso guard 225, elbowprotectors 230, gloves 235, etc., all of which incorporate SMM spacerfabric 105 in their construction. In one preferred form of theinvention, and looking now at FIG. 17, the protective padding 220 maycomprise an outer surface 240 for receiving impact (and which maycomprise a hard plastic, a flexible material, etc.) and an inner surface245 for contacting the body of the wearer (and which may comprise asuitable fabric such as felt). In such a configuration, second fabriclayer 115 of SMM spacer fabric 105 may reside adjacent to (or beattached to) outer surface 240 and first fabric layer 110 of SMM spacerfabric 105 may reside adjacent to (or be attached to) inner surface 245,with yarns 120 spanning the gap between first fabric layer 110 andsecond fabric layer 115. When a force (e.g., the impact of a lacrossball, of a lacross stick, of another player, etc.) contacts outersurface 240, yarns 120 are temporarily compressed, whereby to absorb theimpact and protect the wearer from injury. Because yarns 120 areresilent, when the force is removed, the SMM spacer fabric returns toits original configuration, thereby maintaining its ability to shieldthe wearer from another impact. Thus, SMM spacer fabric 105 is used toform a layer of protective padding for absorbing an impact andprotecting the body of a wearer from injury.

Looking next at FIG. 18, SMM spacer fabric 105 can be incorporated intohip padding 250, thigh padding 255, and torso padding 260 for footballapplications. With the hip padding 250 and thigh padding 255, the outerlayer 240 may comprise the fabric of a uniform, whereas with torsopadding 260, outer layer 240 may comprise a hard plastic.

Looking next at FIG. 19, for a hockey application, SMM spacer fabric 105can be incorporated into collar padding 265, shoulder padding 270, elbowpadding 275, torso padding 280 and/or hip padding 285. As with thelacrosse and football padding discussed above, collar padding 265,shoulder padding 270, elbow padding 275, torso padding 280 and/or hippadding 285 each incorporate SMM spacer fabric 105 between an innersurface 245 and an outer surface 240. Again, outer surface 245 may be ahard plastic (e.g., for collar padding 265, shoulder padding 270, elbowpadding 275 and torso padding 280), or fabric (e.g., for hip padding285).

In still another application, and looking now at FIG. 20, SMM spacerfabric 105 can be incorporated into torso padding 290 and shoulderpadding 295 for mountain biking applications. In the mountain bikingapplication, it is preferred that the outer layer 240 of the protectivepadding be a hard plastic.

It should be appreciated that for any protective padding application,including but not limited to the sporting equipment discussed above, SMMspacer fabric 105 may be used alone or in combination with traditionalpadding. For example, different areas of the protective padding mayincorporate SMM spacer fabric 105 while other areas of the protectivepadding may incorporate traditional padding materials (e.g., foam), orSMM spacer fabric 105 may be used in combination with (i.e., on top ofor beneath) a layer of traditional padding materials (e.g., foam), ormultiple layers of SMM spacer fabric 105 may be used, or any combinationthereof.

Moreoever, different varieties of SMM spacer fabric 105 may be utilized,depending on the desired application. For example, critical areas mayincorporate SMM spacer fabric having longer yarns 120 (and therefore awider gap between first fabric layer 110 and second fabric 115) so as tobe able to better absorb an impact and protect the wearer, while lesscritical areas may incorporate SMM space fabric having shorter yarns 120(and therefore a smaller gap).

Additionally, first fabric layer 110 and second fabric layer 115 canvary depending on the application or area of the equipment on which theyare employed.

Superelastic spacer fabrics can also be formed into clothing so as toprovide protective padded clothing.

Modifications Of The Preferred Embodiments

It should be understood that many additional changes in the details,materials, steps and arrangements of parts, which have been hereindescribed and illustrated in order to explain the nature of the presentinvention, may be made by those skilled in the art while still remainingwithin the principles and scope of the invention.

What is claimed is:
 1. Protective padding comprising: a spacer fabriccomprising a first fabric layer, a second fabric layer, and a pluralityof interconnecting filaments extending between said first fabric layerand said second fabric layer; wherein at least one of said first fabriclayer, said second fabric layer and said plurality of interconnectingfilaments comprise a shape memory material.
 2. Protective paddingaccording to claim 1 wherein said shape memory material is superelastic.3. Protective padding according to claim 2 wherein said shape memorymaterial is Nitinol.
 4. Protective padding according to claim 2 whereinsaid shape memory material is a titanium near-beta alloy.
 5. Protectivepadding according to claim 1 wherein said plurality of interconnectingfilaments comprise a shape memory material.
 6. Protective paddingaccording to claim 5 wherein said plurality of interconnecting filamentscomprise a shape memory material and wherein at least one of said firstfabric layer and said second fabric layer do not comprise a shape memorymaterial.
 7. Protective padding according to claim 5 wherein whereinsaid first fabric layer, said second fabric layer and said plurality ofinterconnecting filaments all comprise a shape memory material. 8.Protective padding according to claim 1 wherein said shape memorymaterial is engineered to have a martensitic state between 0 degrees C.and 90 degrees C.
 9. Protective padding according to claim 1 wherein theshape memory material is engineered to oscillate between phasetransformations so as to maximize its peak dampening characteristics andstorage modulus.
 10. Protective padding according to claim 1 whereinsaid protective padding is contoured so as to provide increased supportto specific regions of a wearer's anatomy.
 11. Protective paddingaccording to claim 10 wherein said contouring is achieved byshape-setting said protective padding using a heating source. 12.Protective padding according to claim 1 wherein voids in said spacerfabric are filled with a material.
 13. Protective padding according toclaim 12 wherein said material is a gel.
 14. Protective paddingaccording to claim 12 wherein said material comprises a polymer capableof transitioning between a solid state and a viscous state due toloading and unloading of said shoe insole.
 15. Protective paddingaccording to claim 1 wherein said shape memory material is coated withsilver to impart antibacterial and antifungal properties to said shapememory material.
 16. Protective padding according to claim 1 whereinsaid spacer fabric is disposed between an outer surface and an innersurface.
 17. Protective padding according to claim 16 wherein said outersurface comprises the shell of a helmet, and said inner surfacecomprises a harness for attaching the shell of the helmet to the head ofa wearer.
 18. Protective padding according to claim 16 wherein saidouter surface comprises a hard plastic.
 19. Protective padding accordingto claim 16 wherein said inner surface comprises a soft material. 20.Protective padding according to claim 1 wherein at least a portion ofsaid spacer fabric is coated with a polymer.
 21. Protective paddingaccording to claim 20 wherein said polymer is Teflon.
 22. Protectivepadding according to claim 20 wherein said entire spacer fabric iscoated with said polymer.
 23. Protective padding according to claim 20wherein only selected portions of said spacer fabric are coated withsaid polymer.
 24. Protective padding according to claim 20 wherein saidpolymer coating is applied to the SMM wire before the SMM wire is knitinto the spacer fabric construct.
 25. Protective padding comprising: anouter surface; an inner surface; and a spacer fabric disposed betweensaid outer surface and said inner surface, said spacer fabric comprisinga first layer, a second layer, and a plurality of interconnectingfilaments extending between said first layer and said second layer;wherein at least one of said first layer, said second layer and saidplurality of interconnecting filaments comprise a shape memory material.